Self-locking electrical plug and socket



June 12, 1962 s. A. WALKER 3,039,073

SELF-LOCKING ELECTRICAL PLUG AND SOCKET Filed March 2. 1959 IN V EN TOR. Jfepfierz A. W7)??? United States Patent Ofiice 3,039,073 Patented June 12, 1962 3,039,073 SELF-LOCKING ELECTRICAL PLUG AND SOCKET Stephen A. Walker, Groton, Conn. (Box 247, Hope, RJ.) Filed Mar. 2, 1959, Set. No. 796,541 13 Claims. (Cl. 339-95) This invention relates to an electrical connector. More particularly, this invention relates to a female plug connector that includes means for automatically locking a male plug in electrical engagement therewith, and means for easily releasing the male plug for separation by relative rotary or lateral movement with respect thereto.

One of the common disadvantages in the conventional female electrical plug connectors in use today is that they are too easily disconnected from the male plug to which they are electrically coupled. Since the conventional female plug connector and male plug are only joined by frictional engagement of the male prongs extending into the slots formed in the female plug, accidental removal of the male prongs from engagement with the female plug is diflicult to prevent.

Prior to the instant invention some attempts have been made to solve the problem, but the resulting plug connector devices have either been too complicated and costly or did not properly function in use. Accordingly, it is an object of the present invention to provide an electrical plug element that is simple in construction, easy to use and effective in operation.

Another object of the present invention is to provide a female plug connector that includes means for automatically looking a male plug therein upon insertion of the male plug prongs through the female plug openings, whereby positive and uninterrupted contact is insured under any and all conditions, thus making the instant invention particularly advantageous and desirable for use with time clocks, automatic controllers and the like.

Still another object is to provide a quick release mechanism for use in a self-locking female plug so that the male plug may be released from electrical contact with the female plug whenever desired.

Still another object is to provide a locking finger in a female plug for automatically engaging and looking a male prong in the female plug when the male prong is inserted therein.

Still another object is to provide a female plug which includes a cover plate that is movable with respect to the body portion of the female plug for effecting the release of a male plug from electrical engagement with the female 111 p ther objects and the nature and advantages of the instant invention will be apparent from the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is an elevational view of the female plug connector, embodied in the present invention, with a male plug shown looked in electrical engagement therewith;

FIG. 2 is an elevational view, with parts shown in section, of the inside of a mating section of the female plug connector illustrated in FIG. 1;

FIG. 3 is a bottom plan view of the cover plate secured to the outer end of the body portion of the female plug connector;

FIG. 4 is a view similar to FIG. 3 with the cover plate removed;

FIG. 5 is a sectional view taken along line 5-5 in FIG. 2;

FIG. 6 is a view of the inside surface of the cover plate;

FIG. 7 is a sectional view taken along line 77 in FIG. 2;

FIG. 8 is a view similar to FIG. 2, with the cover plate and the electrical elements removed from an exposed section of the female plug;

FIG. 9 is a detail view in perspective of one of the contact elements that is positioned in the female plug connector;

FIG. 10 is a detail view in prespective of one of the locking fingers that is secured within the female plug connector;

FIG. 11 is a view similar to FIG. 3 showing a modified form of the invention;

FIG. 12 is a bottom plan view of the modified form of the female plug connector with the cover plate removed;

FIG. 13 is a view of the inside surface of the modified cover plate; and

FIG. 14 is a detail view in perspective of the modified contact member.

Referring now to the drawings, and particularly FIGS. 1 through 10, one form of the present invention is illustrated and comprises a female plug connector generally indicated at 10. As shown in FIG. 1, the female plug connector 10 is adapted to be electrically connected to a two-wire electrical conductor or extension cord 12 and is adapted to receive in electrical engagement therewith a male plug connector indicated at 14. The male plug connector 14 is of conventional construction having a two-wire electrical conductor or extension cord 16 secured thereto and including outwardly extending male prongs 18 (FIG. 2) as is well known in the art. The female plug connector 10 is generally cylindrical in configuration and is defined by a body portion 20 that tapers into a reduced neck portion 22. The plug connector 10 is molded of any suitable non-conductive material, such as Bakelite, in two identical sections, the sections being secured together by a laterally extending stud 24.

Although the male plug connector 14 illustrated herein is of the conventional two-prong type, it will be understood that my invention, hereinafter to be described, is equally adaptable to a plug and socket having any desired number of prongs. Also, the prongs 18 could well be round in cross section, rather than flat, as disclosed, without affecting the basic concepts of my invention. In such a case, the female contacts which receive the prongs would be correspondingly modified, such as by having a center groove to receive and center the prongs or pins, as is convential in various forms of telephone jacks and the like.

Referring to FIG. 2, the female plug connector 10 is illustrated with one of the mating sections removed, thereby exposing the interior of the connector '10 and the electrical elements located the-rein. It is understood that the mating sections of the connector 10 are formed identically and that the recesses (FIG. 8) formed therein during the molding operation to receive the electrical elements are similarly and complementally formed in the removed section.

Formed in the reduced neck portion 22 of the mating sections are recesses that cooperate to form an opening 26, the opening 26 being adapted to receive therein the two-wire electrical conductor or extension cord 12.. S01- dered or joined in any suitable fashion to the leads of the two-wire electrical conductor 12 are spaced contact elements generally indicated at 28'. The contact elements 28, which are illustrated in detail in FIG. 9, are positioned in suitably formed recesses located in the body portion 20 of the plug connector 10 and each includes a foot portion 30, a contacting portion 32 and an intermediate portion 33 joining the foot and contacting portions. Each of the foot portions M of the contact elements 28 is secured to an exposed wire of the two-wire electrical conductor 12 and is thereby disposed in electrical contact therewith.

The contacting portion 32 of each of the elements 28 is positioned in a widened longitudinally extending recess 34, said recess defining a socket for receiving the male prongs 18 of the male plug connector 14. As shown more clearly in FIG. 5 the portion of the recess or sockets 34 that receives the male prongs 18 therein are arcuate in configuration, the purpose of which will be described hereinafter.

As shown in FIG. 9, the contacting portions 32' of the elements '28 have an arcuate configuration and are formed with curved edge portions 36 on one side thereof. The curved edge portions 36 are disposed in slots 37 formed adjacent the sockets 34 that receive the contact elements in position within the body portion 28 but define a pivot point about which the contact elements pivot when the male prongs 18' are thrust into the sockets 34. Referring to FIG. 5, the contact elements are shown biased into engagement with the walls of the sockets 34 by the male prongs 18 that project into the sockets. It is seen that upon removal of the male plug 14 from engagement with the connector 10, as will be described, the male prongs will be withdrawn from the sockets 34 thereby releasing the contact elements for slight pivotal movement about the curved edge portions 36. In this position, the contacting portions 32 of the contact elements 28 project somewhat in the path of the male prongs 18 when they are inserted into the sockets 34 and assure positive engagement between the male prongs and the contact elements. The outermost ends of the contacting portion 32 of the contact elements 28' are also slightly flared outwardly as at 37 (see FIG. 2) which provides for easy insertion of the male prongs 18 into the sockets 34.

In order to prevent the accidental removal of the male prongs 18 from engagement with the contact elements 28, retaining members, generally indicated at 38, are provided and are positioned in suitable recesses formed in the mating sections of the body portion 20. The retaining elements 38, one of which is illustrated in detail in PEG. 10, are formed of structural material such as steel and include a body 39 on which is joined an outwardly turned end section 40, the end section 48 being adapted to lock the retaining elements 38 within the body portion 20 of the connector 18. Formed on the other end of the retaining elements 38 and inclined at an arcuate angle with respect to the body 39 are fingers '42. The fingers 42 terminate in knife edges 44 that are spaced from the contacting portion 32 of the contact elements 28. Because of the inclination of the fingers 42, the male prongs 18 may be easily pushed into the sockets 34 and into electrical engagement with the contact elements 28, it being apparent that the resilience of fingers 42 will function to further insure that the male prongs are forced into good electrical engagement with contacts 28. At the same time, it will be seen that the knife edges 44 bite into the adjacent surfaces of the male prongs 18 and grip the prongs, thereby preventing the prongs from being pulled outwardly from the sockets 34. It will be understood that the retaining elements 38 could be an integral part of the contact ele- 'rnents 28, or in the alternative they could be constructed of electrically conductive material. As aforementioned, however, it is desirable that the elements 38 be durable and ruggedly resilient, and hence I prefer to construct them of steel or the like.

In order for the male prongs 18 to be removed from engagement with the contact element 28 when it is desired to disengage the male connector 14 from the female plug connector 10, the male prongs 18 are rotated within the arcuate sockets 34 with respect to the retaining elements 38 so as to become completely disengaged therefrom whereupon the male plug may be easily and freely separated from the female plug. In order to rotate the male plug and prongs 18, a cover plate 46 is provided which, as shown in FIG. 3, includes openings 48 that normally communicate with the sockets 34 and are adapted to receive the male prongs 18 therein. A central opening is also formed in the cover plate through which a threaded bolt 58 is inserted for engagement with a threaded opening 52 formed centrally in the body portion 20 of the female plug connector 10. The cover plate 46 is movable with respect to the bolt 50 and is thereby rotatable relative to the body portion 28.

The cover plate 46 is normally located in the position as shown in FIG. 2, in which position the male prongs 18 are disposed in electrical engagement with the contact elements 28. When the cover plate 46 is rotated with respect to the plug connector 10, it is necessary that it be returned to its normal position after the male prongs 18 have been removed from engagement with the contact elements 28. In order to provide for automatic return of the cover plate 46 to the normal position thereof, a spring 54 is provided and is disposed in an annular recess 56 formed in the body portion 20. The spring 54 is formed with an end prong 58 that extends into a slot located in the cover plate 46 and is also formed with an oppositely disposed end prong 68 that extends into a similar slot formed in the body portion 20. It is seen that upon rotation of the cover plate 46 with respect to the body portion 20 of the female plug connector, the spring 54 will be biased; and upon release of the cover plate 46, it will automatically return to the normal position thereof.

In order to guide the rotary movement of the cover plate 46 as it is moved with respect to the body portion 28 and so that it will always follow the same rotary path, an arcuate slot 62 is provided and is formed in the outer surface of the body portion 20. The arcuate slot 62 receives therein a protuberance 64 that is formed on the inner surface of the end plate 46, and it is seen that upon rotary movement of the cover plate 46, the protuberance 64 will move within the arcuate slot 62 and will be guided thereby. It is further understood that the slot 62 also defines the limit of rotary movement of the cover plate 46.

In use, the male plug 14 is electrically connected to the female plug 10 by inserting the male prongs 18 through the cover plate openings 48 and into the sockets 34 formed in the body portion 28. As the male prongs move into the sockets 34 they are guided between the knife edges 44 of the retaining elements 38 and the contacting portions 32 of the contact elements 28. The contacting portions 32 are biased against the walls of the openings 34 by the male prongs 18 thereby assuring positive electrical contact between the male prongs 18 and contact elements 28. Once the male prongs 18 have been inserted the full length thereofinto the openings 34, they are locked therein by the inwardly inclined knife edges 44 that grip the surfaces of the male prongs 18. It is seen that removal of the male plug 14 from the female plug connector 10 isprevented and that the more force exerted in pulling outwardly on the male plug 14, the more tightly the prongs 18 will be gripped by the knife edges 44.

In order to remove the male plug 14 from engagement with the female plug connector 18, the male plug 14 and the cover plate 46 are rotated with respect to the body portion 28, whereby the male prongs 18 are rotated counterclockwise, as seen in FIG. 5, out of engagement with the contact elements 28 and the retaining elements 38. As soon as the male prongs 18 clear the contact elements 28 and the retaining elements 38, the male plug 14 may be removed from engagement with the female plug connector 18 by simply pulling outwardly thereon. When the male prongs 18 have been removed from the sockets 34 and are free of the cover plate openings 48, the spring 54, which had been biased upon rotation of the cover plate 46, will automatically return the cover plate 46 to the original position thereof.

Although it is desirable, for the reasons hereinbefore described, that the contacts 28 be arcuate in cross section, it is emphasized that such is not essential because the fiat prongs 18 are generally narrow enough so that they may be easily rotated sideways from between contacts 28 and retaining elements 38 whether the former are arcuate or flat.

If for any reason it should ever become necessary or desirable to rotate male plug 14 and prongs 18 back into engagement with contacts 28 after disengagement therefrom but before separation of plugs and 14, male plug 14 may be rotated clockwise, viewing FIG. 5, assisted by spring 54, back into engaged position. During such reversing movement, flared edge portions 36 and bevels 43 on fingers 42 will facilitate re-entry of prongs 18 back between contacts 28 and retaining members 38.

Referring now to FIGS. 11 through 14, a modified form of the invention is illustrated and generally includes the structural details as described above in connection with the invention illustrated in FIGS. 1 through 10. In the modified form of the invention, the cover plate is adapted to be moved laterally with the male prongs 13 with respect to the connector 10, rather than rotatably, and in order to accommodate this movement, the body portion is formed with extra-width sockets 66 as shown in FIG. 12. Formed in the body portion adjacent the sockets 66 are recesses 68 and 70 which receive therein contact elements 72 and retaining elements 74, respectively. Additional laterally extending recesses 76 are formed in the body portion 20 and receive springs 78 therein, the purpose of which will hereinafter be set forth.

As shown in FIG. 14, the contact elements 72 are formed with curved edge portions 80 on both lateral edges of the contacting portion thereof, thereby providing a slightly biasing effect of the contacting portion toward the socket 66. It is also seen that by forming the curved edge portions 80 on both lateral edges of the contacting portions of the contact elements 72, the contact elements 72 may be interchangeably positioned within the assembly.

Referring to FIGS. 11 and 13, the modified cover plate is indicated at 82 and is formed with spaced openings 84 that are normally aligned with the portion of the sockets 66 adjacent the contact elements 72 and retaining elements 74, said retaining elements being generally identical to the elements 38 aforedescribed. Formed in the cover plate 82 between the openings 84 is a slot 86 through which extends a bolt 88. The cover plate is movable with respect to the bolt 88 and it is seen that this movement is confined to the limits of the slot 86. The bolt 88 is threadably received in an opening 90 formed centrally in the end surface of the body portion 20. As shown in FIG. 13, the underside of the cover plate 82 has protuberances 92 formed thereon that project into the slots 76 and engage the spring 78. The springs 78 thus act to retain the cover plate 82 in the normal position thereof and will be biased upon lateral movement of the cover plate.

In use, a male plug is electrically united with the modified female connector by simply inserting the male prongs through the cover plate openings 84 and into the sockets 68 whereby electrical contact is made with the contact elements 72. The curved edges 80 tend to bias the contact elements into positive engagement with the male prongs 18, said male prongs, in turn, being biased against contacts 72 by the resilience of the knife edge extensions of retaining elements 74. The knife edges of the retaining elements 74 engage the surfaces of the male prongs in the same manner as hereinbefore described and thereby prevent the removal thereof in this position. In order to remove the male plug from engagement with the female connector, the cover plate 82 and male plug are shifted laterally thereby moving the male prongs within the sockets 66 to the dotted-line position shown in FIG. 12. In this position the male prongs have cleared the retaining elements 74 and are free for extraction from the sockets 66. Since the springs 7 8 were biased by the protuberances 92 during the lateral movement of the cover plate 82, once the male prongs are free of the cover plate openings, the springs 78 will automatically return the cover plate 82 to its normal position. If it should ever be necessary or desirable to slide the male prongs back into engagement with contacts 72, after disengagement therefrom but before separation of the plugs, it will be seen that the curved or flared edges 80 will facilitate re-entry of the prongs back between the contacts and retaining elements, just as is the case in the first form of my invention.

It will be understood that in both forms of my invention the basic concept is the same, namely, to disengage the male prongs from the locking means by virtue of a lateral movement of the male plug with respect to the body portion of the Iemal plug. In the preferred form of my invention the lateral movement is rotary, whereas in the embodiment of FIGS. 11 through 14, the lateral movement is linear.

In both cases, however, it has been found that my invention contributes to the provision of a plug and socket having an extended life in operation, as compared to conventional plugs and sockets. More specifically, it has been found that in conventional plugs and sockets, arcing at the tips draws the temper and erodes the metal, thus shortening the effective life of the receptacle. Side breaking contacts, however, as per my invention, provide a wide arcing area, thereby weakening the arc and dissipating the heat rapidly, whereby the tendency for the contacts to erode is greatly lessened.

It will be obvious to those skilled in the art that various changes may be made without departing from the spirit of the invention and therefore the invention is not limited to what is shown in the drawings and described in the specification, but only as indicated in the appended claims.

What is claimed is:

1. In an electrical connector, identical sections secured together and defining a body portion for receiving a conductor therein, a pair of spaced contact elements positioned in said body portion and electrically connected to said conductor, a pair of retaining elements positioned in said body portion and including knife edges facing in the direction of said contact elements, longitudinally extending sockets formed in said body portion between said contact elements and said retaining elements, a cover plate secured for relative movement to said body portion, openings formed in said cover plate and communicating with said sockets, said openings and sockets being adapted to receive prongs extending from a male plug whereby when said prongs are thrust into said body portion they extend between said contact and retaining elements and are locked against outward thrust by said knife edges, said cover plate being normally positioned so that the openings therein are in alignment with said sockets, said cover plate and said male plug being movable as a unit to laterally shift said prongs out of locking engagement with said knife edges, whereby said male plug is freed for detachment from said electrical connector, and spring means normally biasing said cover plate to the locking position wherein said openings are in alignment with said sockets.

2 In an electrical connector adapted to be electrically joined to a male plug having electrically conducting prongs projecting outwardly therefrom, said connector including a body portion having a cover plate secured to said body portion and movable relative thereto and having slots formed therein, longitudinally extending sockets formed in the body portion and adapted to receive the male prongs therein, electrically conducting means normally communicating with said sockets and adapted to normally engage the male prongs when the latter are thrust through said slots and into said sockets, means in said body portion for normally locking the male prongs against an outward pull whereby the prongs are normally maintained in electrical cont-act with said electrically conducting means, said cover plate and male plug being laterally movable as a unit relative to said body portion to release said prongs from engagement with said locking means, whereupon said m-ale plug may be freely pulled away for detachment from said connector, and means normally biasing said cover plate to the position wherein said slots are aligned with said sockets.

3. In an electrical connector for use with a male plug having prongs, a body portion having one end portion formed with an opening for receiving a conductor cable therein, longitudinally extending sockets formed in said body portion adapted to receive said prongs therein, contact elements positioned in said body portion adjacent said sockets and electrically connected to said conductor cable, said prongs being adapted to engage said contacts when inserted into said sockets for making electrical contact therewith, means carried by said body portion engaging said male prongs in said sockets for normally retaining said prongs against an outward pull and in contact with said contact elements, and a cover plate secured to the opposite end of said body portion, said cover plate includ ing openings of a size just sufficient to receive said prongs, said cover plate normally being positioned so that said openings are in alignment with said contact elements and said retaining means but being movable with respect to said body portion to a position wherein said openingsare disaligned with respect to said contact elements and: retaining means, whereby said male plug and cover plate may be moved as a unit to laterally disengage said prongs from said retaining means so that the male plug may be freely withdrawn from said body portion.

4. In an electrical connector as set forth in claim 3, said cover plate and said male plug being rotatable with respect to said body portion to release said male prongs from engagement with said retaining means.

5. In an electrical connector as set forth in claim 3, said cover plate and male plug being laterally movable in a linear path with respect to said body portion to release said male prongs from engagement with said retaining means.

6. In an electrical connector adapted to be electrically joined to a male plug having electrically conducting prongs projecting outwardly therefrom, longitudinally extending sockets formed in said connector for receiving said prongs therein, contact elements located in said connector and adapted to normally engage said prongs when they are inserted into said sockets, means in said connector for locking said prongs against an outward pull and in electrical contact with said contact elements, a cover plate including openings of a size just sufiicient to receive said prongs, said cover plate normally being positioned so that said openings are in alignment with said contact ele ments and said retaining means but being movable with respect to said body portion to a position wherein said openings are disaligned with respect to said contact elements and retaining means, whereby said male plug and cover plate may be moved as a unit to laterally disengage said prongs from said retaining means so that the male plug may be freely withdrawn from said body portion, and means normally biasing said cover plate to its aligned position.

7. In an electrical connector as set forth in claim 6, said cover plate and said male plug being rotatable with respect to said connector to laterally release said prongs from engagement with said locking means.

8. In an electrical connector as set forth in claim 7, said sockets being arcuate in cross-sectional configuration for accommodating said prongs during the rotatable movernent of said male plug with said cover plate.

9. In an electrical connector as set forth in claim 6, said cover plate and male plug and prongs being laterally movable in a linear path with respect to said connector to release said prongs from engagement with said locking means.

10. In an electrical connector as set forth in claim 9, said sockets being widened laterally for accommodating said prongs during the linear lateral movement thereof with said cover plate.

11. In an electrical connector adapted to be electrically joined to a male plug having electrically conducting prongs projecting outwardly therefrom, contact means positioned in said connector and adapted to electrically engage said prongs when they are inserted Within said connector, means in said connector for engaging said prongs and preventing their withdrawal from said connector, and a cover member secured for relative movement to said connector and having openings through which said prongs extend, said cover member and male plug being movable as a unit and relative to said connector to release said prongs from engagement With said engaging means and to break electrical contact of said prongs with said contact means, whereby said male plug is free for withdrawal from said connector, said engaging means comprising a blade extending in substantially parallel spaced relation with respect to said contact means and having a gripping finger extending toward said contact means from the end of said blade most closely adjacent said cover member, said finger making an acute angle with said blade and being adapted to dig into said male prongs to prevent Withdrawal thereof, and spring means carried by said connector and engaging said cover member for normally biasing said cover member to the position wherein said openings therein are in alignment with said contact means.

12. In an electrical connector as set forth in claim 11, said cover member being rotatable with respect to said connector to release said prongs from engagement with said engaging means.

13. In an electrical connector as set forth in claim 11, said cover member being laterally movable in a linear path with respect to said connector to release said prongs from engagement with said engaging means.

References Cited in the file of this patent UNITED STATES PATENTS 2,043,247 Hubbell June 9, 1936 2,102,625 Hubbcll Dec. 21, 1937 2,609,416 Cousins Sept. 2, 1952 2,641,627 Lewis June 9, 1953 2,820,842 Meistrell Jan. 21, 1958 

